The present invention relates to a color image forming apparatus and, more particularly, to a color image forming apparatus promoting efficient maintenance and easy handling of a paper jam.
An electrophotographic color image forming apparatus, as distinguished from a monochromatic image forming apparatus, needs a plurality of developing units each assigned to a particular color, e.g., one of yellow, magenta, cyan, and black. Further, a color image forming apparatus involves a sophisticated process including development and image transfer with different colors being superposed one above the other and the fixation of laminate toner. In addition, developers of different colors must be replenished from time to time. On the other hand, a photoconductive element or image carrier and an intermediate transfer body included in the apparatus are frequently replaced, so that measures against paper jams are necessary. In these circumstances, there is an increasing demand for an image forming apparatus promoting efficient maintenance and easy handling of a paper jam.
Japanese Patent Laid-Open Publication No. 5-323690, for example, discloses a color image forming apparatus having a clamshell type structure made up of an upper body part and a lower body part. The upper body part is movable, or openable, about a shaft away from the lower body part. A photoconductive belt and a case accommodating developing units are constructed into a cartridge. The cartridge is mounted to the apparatus while being positioned relative to a laser writing unit. When a paper or similar recording medium jams a transport path, the operator opens the upper body part away from the lower body part in order to uncover the path and then removes the paper.
However, a problem with the above clamshell type apparatus is that the upper body part is bulky and heavy and thereby difficult to operate. Further, a sufficient space for removing a jamming paper is not available with the apparatus. Moreover, removing a jamming paper under such a heavy article is not desirable from the safety standpoint. In addition, the cartridge including the belt and developing units is bulky and difficult to replace.
Japanese Patent Laid-Open Publication No. 2-262676 teaches a color image forming apparatus including a photoconductive belt and developing units constructed into a cartridge removable from the apparatus. A transport path for transferring an image to a paper or similar recording medium is formed above the belt. A cover covering the transport path is openable upward away from the belt. After the cover including an image transfer section has been opened upward, the above cartridge is removed sideways for replacement. This, however, cannot be done without resorting to sufficient spaces above and at the side of the apparatus that originally has a substantial size. As a result, a broad space is necessary for the installation of the apparatus. In addition, the cartridge is bulky and awkward to replace.
Japanese Patent Laid-Open Publication No. 8-211816 proposes a color image forming apparatus including a top cover. When the top cover is opened, a cartridge including a photoconductive element and developing units can be moved upward in order to uncover a transport path. With this kind of apparatus, the operator intending to remove a jamming paper must open the top cover and then lift the cartridge including the photoconductive element and developing units. This obstructs efficient maintenance.
Japanese Patent Laid-Open Publication No. 7-325444 discloses a color image forming apparatus including a top body part openable upward about a shaft mounted on the rear portion of the apparatus. A unit including a photoconductive element and an intermediate transfer body is removably mounted to the upper body part. A cover is mounted on the top body part and may be opened in order to remove a jamming paper. This apparatus has a drawback that although the photoconductive element and development units are constructed integrally, a paper jamming an image transfer station must be dealt with at the top rear side of the apparatus, resulting in troublesome work. Moreover, the apparatus gives no consideration to a paper jam apt to occur just after a paper cassette. In addition, because printings are driven out to the rear of the apparatus although face up, the apparatus needs a broad space and renders the handling of printings awkward.